This invention relates generally to improvements in a filter-drier unit, and more particularly to a bidirectional flow filter-drier unit for use in the liquid line of reverse-cycle refrigeration and air-conditioning systems, more commonly known as heat pumps.
There are many filter-driers which have been and can be used in heat pumps, but these filter-driers are designed for refrigerant flow in one direction only so that if there is a backflow, solid contaminants that were picked up in the forward flow direction are released to the system. Consequently, the use of these filter-driers requires the use of two such filter-driers in the liquid line with suitable bypass valves and piping that restrict flow in one direction or requires additional liquid line piping in association with bypass valves when a single filter-drier is utilized.
Another type of bidirectional flow filter-drier assembly is disclosed in U.S. Pat. No. 4,029,580 in which a pair of filter-drier units are provided in a single shell, each filter-drier unit being located in its own compartment at one side of a partition, and being provided with a suitable check valve and with a flow inlet port in the partition to assure flow through only one filter-drier unit in each direction of flow through the shell.
Another type of filter-drier assembly adapted for bidirectional flow in heat pump systems is disclosed in U.S. Pat. No. 4,104,044, wherein a bypass line circumvents each expansion device located in the liquid line, and a filter-drier unit is disposed in each bypass line, the assembly including a check valve enabling flow through the associated bypass line and filter-drier unit in one direction only.